Method of making flat-bottomed cathode ray tubes



K. DIELS 2.178.226 METHOD OF MAKING FLAT-BOTTOMEQ CATHODE RAY TUBESFiled Sept. 24, 1957 INVYENTOR KURT D/ELS ATFORNEY Patented Oct. 31,19392,178,226

Kurt Diels,'Berlin, Germany, assignor to Telefunken Gesellschaft fiirDrahtlose Telegraphic in. b. H Berlin, Germany, a corporation of GermanyApplication September 24, 1937, Serial 1%.,165430 lin Germany July 16,1936 2 Claims.

They. present invention is concerned with a method of manufacturingcathode ray tubes hav ing a flat bulb bottom. r

The customary'form of cathode ray'tube of 5 the kind used, for instance,for television work consists of a cone-shaped flaring bulb which isclosed by a curved bottom which mostly supports the luminescent orfluorescent substance (phosphor).

fiat disk is welded onto the end of the bulb.

However, the manufacture of such bulbs is rather For reasons ofruggedness andv far greater than with bulbs with a curved bottom whichcan be made in one piece. Now, the present invention discloses anextremely simple method of manufacturing tubes having a flat bottom ofthe kind used particularly for television work. According to theinvention, the bulb of the-tube including the'fiat closure or end diskthereof is "made by blowing, in one working stage, a heated glassparison against a flat metal surface while the remaining portions of thegob are unconfined, and retaining the glass in such position until ithardens.

- KURT DIELS.

strength a curved bottom has proved most ad- (gob) when in plastic stateagainst a flat sur- 10 vantageous in these tubes or bulbs for this makesface preferably consisting of metal.- It has been it feasible to makethe bottom of comparatively discovered that if the glass gob is blownagainst thin glass; and if the bulb of the tube is conical, asufliciently flat surface, the surface produced the change from or theconnection between the in the interior of the bulb will turn out so flat15 bottom of the bulb and the sides carrying the and smooth that notrace of distortion is nobottom may be so formed that the risk ofbreakticeable. A tube or bulb manufactured by the age is minimized. 3method of this invention is eminently suited also However, the curvatureof the bulb bottom, for projection Work- It has also been When viewing apicture oscillogram or the like itained that especially when a hardvariety of I delineated upon the bottom of the bulb proves glass isemployed in making the bulb and if care extremely annoying on the groundthat in adis taken so that the smooth and flatbulb surdition to thereflection of light reaching the face is heavier and thicker than thelateral walls viewer's eyes from the convex glass surface,- the of thebulb, the risk of breakage will be extremely ,image seems subject tothefbarrel" type of dissmall. 26 tortion. Also in the case of aprojection f a, Figs. 1 and 2 are partial elevations of the tubefluorescent Screen e, abulb bottom which bulb in the course ofproduction and in finished is convex in reference to the imaging lens isstate. Referring to the drawing, l denotes the very unsuited. For thisreason, compensatory g s bu 2 is the l Surface a a st which 30 opticallenses have been suggested in the prior he b is ew W n in h p a e; 80art both in the case of directviewing as well by the agency of an 'b aacting in e lilas in the case of optical projection of fluorescent Yl'eetien 0f the arrow so that a tube havinga screen pictures.Particularly where compensat- 'l y flat bottom ensues the kind Shown inglenses of large diameters are required for in I 5 the saidpurpose, meansof the said kind are W I claim 15! very costly. 'Because of all of thesedisadvan- The method of makmg a 5 tube tages and difliculties-inherentin the use of bulbs having fiat end well which mPr1seS the Steps havingcurved bottoms it has been felt very deblowmg a glass heated Plasticstate sirable to create a flat bottomed bulb, so much 31 its i q fi g sigg fi 40 more so that as changes in the size of the spot 6 remammg 9 18 O are 4 occurring in this case may be rendered negligible g igi aig ggthe glass to harden wmle' g g? the a i EP di- 2. The method of making acathoderay tube e y ng Sm e e ron op having a con1cal'body portion and aflat end wall 'Ifubes or bulbs known m the prior art which comprises thesteps of blowing a heated Y 45, which the bottom in the form of a planaror and plastic t; of glass with its closed end

